Tunnel detection by way of a detection system comprising cameras in a vehicle is known. This detection is generally based on signpost recognition. Tunnel detection makes it possible to adjust driving assistance devices when the vehicle travels into the tunnel. If the cameras for detecting the tunnel fail, it becomes no longer possible to adjust the driving assistance devices when the vehicle travels into the tunnel. For economic reasons, some vehicles are not equipped with road-monitoring cameras.
One known alternative for tunnel detection is tunnel detection using a radar signal. However, this alternative is not very robust and may feedback incorrect information to the driving assistance devices. The most critical example relates to an incorrect detection of an obstacle on the path of the vehicle instead of a tunnel detection. Specifically, in this erroneous situation, if the vehicle is equipped with an automatic emergency braking function, this function may be incorrectly triggered since the vehicle is simply in a tunnel whose structure causes reflections of radar waves to be falsely interpreted as being the presence of an obstacle on the path of the vehicle.